INTRODUCTION TO COMPUTERS
COMPUTER
Computer is a electronic device which can store, process and retrieve data as and when required. Some times it is also called as data processor.
Characteristics of Computer
Speed
A computer is a very fast device. It can perform in a few second the amount of work that a human being can do I an entire year- if he worked day and night and did nothing else.
While talking about the speed of computer, we do not in talk in term of second or even milliseconds (10-3). Our unit is sped are microseconds (10-6), nanosecond (10-9) , and even picoseconds (10-12). A powerful computer is capable of performing about3 to 4 millions simple arithmetic operations per second.
Accuracy:
The accuracy of a computer is consistently high and degree of accuracy of a particular computer depends upon its design. But for a particular computer, each and every calculation is performed with same accuracy.
Diligence:
Unlike human being, a computer is free from monotony, tiredness, lack of concentration, etc and hence can work for hours together with creating any error and grumbling.
Versatility:
Versatility is one of the most wonderful thing about computer. One moment, it is preparing result of particular examining, the next moment. It is busy in preparing electricity bills, and in between, it may be helping an office secretary to trace an important letter in seconds. Briefly, a computer is capable of performing almost any test provided that the task can be reduced to series of logical steps.
Power of Remembering:
A computer can store and retrieve any amount of information because of its secondary storage capability. Every piece of information can be retained as long as desired by the under and can be recalled as and when required.
No. I. Q.
A Computer is not magical device. It can only tasks that a human being can. The difference is that it performs these talks with unthinkable speed and accuracy. It possesses no intelligence of its own. Its I.Q. is Zero, at least till today. It has to told what to do and in what sequence.
No. feelings:
Computer is devoid of emotions. They have no feelings because they are machine. Although men have successes in building a memory for the computer, but no computer possesses the equivalent of human heart and soul. Computer cannot make such judgments on their own. Their judgment is based on instructions given to them in the form of proems that are written by us. They are only as good as man makes and uses them.
THE EVOLUTION OF COMPUTER
Automatic sequence controlled calculator was the first fully automatic calculating machines designed by Howard A in collaboration with IBM (International Business Machines) corporation.
THE ENIAC (1943-46)
The Electronic Numerical Integrator and Calculator (ENIAC) was first all electronic computer. It was constructed at the Moore school of Engineering of the University of Pennsylvania, U.S.A. BY A DESIGN TEAM LED BY Professor J. Presper Eckert and John Mauchly.
ENIAC was developed as a result of military need. It took up the wall space in a 20 x 40 square feet room and used 18000 vacuum tubes. The addition of two numbers was achieved in 200 microseconds and multiplication in 2000 microseconds.
THE EDVAC (1946-52)
The operation of ENIAC was seriously handicapped by wiring board. This problem was later overcome by the new concept of “stored program” developed by Dr John Von Neumann. The basic idea behind the stored program concept is that a sequence of instructions as well as date can be stored in memory of the computer for the suppose of automatically directions the flow of operation. The Electronic Discrete Variable automatic Computer (EDSAC). The machine executed its first program in May 1949. In this machine, addition operation was accomplished in 1500 microseconds, and multiplication operation in 4000 microseconds. The machine was developed by a group of scientists headed by Professor Maurice Wilkes at the Cambridge University.
THE UNIVAG 1 (1951)
The Universal Automatic Computer (UNIVAC) was the first digital computer which was not “one of its kind”. Many UNVAC machines were produced, the first of which was installed in the Census Bureau in 1951 and was continuously for 10 years. The fist Business use of the computer, a UNIVAC I was by General Electric Corporation in 1954.
In 1952, the International Business Machines (IBM) Corporation introduced the 701 commercial computers. In rapid succession, improved models of UNIVAC I and other 700 series machines were introduced. In 1953, IBM Produced the IBM-650 and sold over 1000 of these computers.
THE COMPUTER GENERATIONS
Generation in computer talk is a step in technology. It provides a frame work for the growth of the computer industry. Originally, the term generation was used to distinguish between varying hardware technologies, But now a days, it has been extended to include both the b=hardware and software which together make up an entire computer system.
FIRST GENERATION (1942-1955)
The first generation computers were ENIAC, EDVAC, and EDSAC etc. These machines and other of their time were made possible by the invention of “vacuum tubes”. These vacuum tube computers are referred to as first generation computers.
Advantages:
1. Vacuum tubes were the only electronic components available during those days.
2. Vacuum tube technology made possible the advent of electronic digital computers.
3. These computers were the fastest device of their time.
Disadvantages:
1. Too bulky in size.
2. Unreliable
3. Thousands of vacuum tubes were used emitted large amount of heat and burnt out frequently.
4. Air conditioning required, constant maintenance required.
5. No portable limited commercial use.
SECOND GENERATION (1955-1964)
The transistor, a smaller and more reliable successor to the vacuum tube, was invented in 1947. However, computers that used transistors were not produced in quantity until over a decade later. The second generation emerged with transistors being the brain of the computer.
Advantages:
1. Smaller in size as compared to first generation computers.
2. More reliable
3. Less heat generated
4. These computers were able to reduce computational times from milliseconds to microseconds.
5. Less prone to hardware failures.
6. Better portability
7. Wider commercial used
Disadvantages:
1. Air-conditioning required
2. Frequent maintenance required
3. Commercial production was ridicule and costly.
THIRD GENERATION (1964-75)
The third generation computer was based on IC (Integrated Circuits) technology and the computes that were designed with the use of integrated circuits were called third generation computers.
Advantages:
1. Smaller in size as compared to previous generation computers.
2. Even more reliable than seconds generation computers.
3. Even lower heat generated than second generation computers.
4. These computers were able to reduce computational times from microseconds to nanoseconds.
5. Maintenance cost is low because hardware failures are rare.
Easily portable
6. Totally general purpose. Widely used for various commercial applications all over the world.
7. Commercial production was easier and cheaper.
Disadvantages:
1. Air-conditioning required in many cases.
2. Highly sophisticated technology required for the manufacture of IC chips.
FOURTH GERNARATION (1975 ONWARDS):
Initially, the integrated circuits contained only about ten to twenty components. This technology was named small scale integration (SSI). Later, with the advancement in technology for manufacturing ICs, it become possible to integrate unto
a hundred components on a single chip. This technology came to be known as medium scale integration (MSI). Then came the era of large scale integration (LSI) when it was possible to integrate over 30,000 components onto a single chip. Efforts is still on for further advancement as it is expected that more than million components will be integrate on a single chip known as very large scale integration (VLSI).
A fourth generation computer, which is what we have now has LSI chips as its brain. It is LSI technology which has led to the development of very small but extremely powerful computer. It was the start of a social revolution; A whole computer circuit was soon available on a single chip, size of a postage stamp.
Advantages:
1. Smallest in size because of high component density
2. Very reliable
3. Heat generated is negligible
4. No air conditioning required in most cases.
5. Much faster in computation than previous generation.
6. Hardware failure is negligible and hence minimal maintenance is required.
7. Easily portable because of their small size.
8. Totally general purpose
9. Cheapest among all the generations.
Disadvantages:
1. Highly sophisticated technology required for the manufacture of LSI chips.
FIFTH GENERATION (YET TO COME):
Scientist are now at the work on the fifth generation computers- a promise, but not yet a reality. They aim to bring us machines with genuine I.Q. , the ability to reason logically, and with real knowledge of the world. Thus unlike last four generations with naturally followed its predecessor, the fifth generation will be totally different, totally novel, totally new.
BASIC COMPUTER ORGANIZATION:
All computer system performs five basic operations:
Inputting: The process of entering data into the computer system.
Storing: Saving data and instructions so that they available for initial or for additional processing as and when required.
Processing: Performing arithmetic operations on the data in order to convert them into useful information.
Outputting: The process of producing useful information or results for the user, such as a printed or visual display.
Controlling: Directing the manner and sequence in which all of the above operations are performed.
The internal architectural design of computers differs from one system to another. However, the basic organization remains the same for all computer system. A block diagram of the basic computer organization is shown in the Fig. 1. In this figure, the solid lines are used to indicate the flow of instruction and data, and the dotted lines represent the controlled exercised by the control unit.
It displays the five major building blocks, or functional units, of a digital computer system. These five units corresponds five basic operations performed by all computer systems. The function of each of these units is described below.
INPUT UNIT:
Input unit performs the following functions.
It accepts (or reads) the list of instructions and data from the outside world.
It converts these instructions and data in the computer acceptable form.
It supplies the converted instructions and data to the computer system for further processing.
OUT PUT UNIT:
Output unit performs the following functions.
It accepts the results produced by the computer which are coded form and hence cannot easily understand by us.
It converts these coded results to the acceptable (readable) form.
It supplies the converted results to the outside the world.
Data
Central
Processing Unit
Fig. 1. : Basic organization of a computer system.
STORAGE UNIT:
The specific functions of the storage units are to holds (store) :
All the data to be processed and instructions required for processing (receive from input device).
Intermediate results of processing
Final results of processing before these results are released to an output device.
d) ARITHMETIC LOGIC UNIT:
The arithmetic and logic unit (ALU) of the computer system is the place where actual execution of the instruction takes place during the processing operation. To be more precise, all the calculations are performed and all comparisons (decisions) arte made in ALU. The data and instructions, stored in the primary storage prior to processing, are transferred as and when needed to ALU where processing takes place. No processing is done in primary storage unit. Intermediate results generated in the ALU are temporarily.
THE SYSTEM CONCEPT
A system is a group of integrated parts that have the common purpose of achieving some objectives. So, the following three characteristics are key to a system.
A system has more than one element.
All the elements of a system are logically related.
All the elements of a system are controlled in such a way that the system goal is achieved.
NUMBER SYSTEM
The number system are basically of two types; non-positional and positional.
Non positional Number System:
In early days, human beings counted on fingers. When ten fingers were not adequate, stones, pebbles, or sticks were used to indicted values. This method of counting uses an additive approach. In this system, we have symbols such as I for 1, II for 2, III for 3, IIII for 4, IIIII for 5 etc. Each symbol represents the same value regardless of its position in the number and symbols are simply added to find out the value of a particular number. Since it is vary difficult to perform arithmetic with such a number system, positional number systems were developed as the centuries passed.
Positional Number:
In the positional number system, there are only a few symbols called digits, and these symbols represent different values depending on the position they occupy in the number. The value of each digit in such a number is determined by three considerations: the digit itself, the position of the digit in the number, and the base of the number system (where base is defined as the total number of digits available in the number system).
The number system that we use it our day-to –day life is called the decimal number system. In this system, the base is equal to 10 because there are altogether ten symbols or digits (0,1,2,3,4,5,6,7,8,9) used in this system. In this system the successive positions to the left of the decimal points represents units, tens, hundreds, thousands etc. Here each position represents a specific power to the base (10). For examination, the decimal number 2586 (written as (2586) 10 consists of the digit 6 in the unit position, 8 in the ten position, 5 in the hundreds position and 2 in the thousands position and its value can be written as:
(2x1000) + (5x 100) + (8 x10) +6
or 2000 + 500 + 80 +6
or 2586
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